NORTH STAFFOEDSHIRE COAL FOSSILS. 203 



sitch Moss, Shafferlong, and Biddulph basins. At 

 Knypersley reservoir, the shale which lies between the 

 Winpenny and Four-foot coals crops out and contains a 

 great abundance of Aviculopecten papyraceus. Of the 

 Dimyaria, there are two groups, one, marine and the other 

 brackish or fresh-water. Of the former, Axinus has only 

 been found. The brackish or fresh-water group is repre- 

 sented by the genera Anthracosia, Anthracoptera, and 

 Anthracomya. Anthracosia is the commonest and most 

 widely-distributed fossil : seven or more species of this genus 

 have been found. It first appears in a bed of clay or marl 

 a little above the Millstone Grit, and is found (with the 

 exception of the two marine beds) in all our fossiliferous 

 beds from the lowest to the uppermost. Anthracosia has 

 been referred to different divisions of the bivalve mollusca. 

 Professor King, who gave it its present name, has shown 

 that it belongs to the unio family. The late Mr. Salter 

 was of opinion that Anthracosia was a burrowing shell. In 

 the soft black shale which overlies the Cockshead ironstone 

 at Adderley Green, great numbers of these shells occur. We 

 have frequently found them in this bed in a vertical position. 

 In the Nova Scotia coalfield shells of this group are abundant. 

 Principal Dawson, of Montreal, who has paid much attention 

 to the fossils of this coalfield, is of opinion that they were 

 brackish or fresh-water shells allied to Mytilidas or to 

 Embryonic Unionidas. He adds, that " the mode of their 

 occurrence precludes the idea that they were burrowers, 

 but favours the belief that they were attached by a byssus 

 to sunken or floating timber." (Quart. Jour. Geol. Soc., vol. 

 xxii., p. 144). Anthracoptera is represented by five species. 

 It had not such a wide range in time as Anthracosia, 

 being almost confined to the Lower thick measures. In 

 the roof of the Hard mine coal this genus is abundant. 



